This invention relates to transmission families and, more particularly, to a family of transmissions having three planetary gearsets and six torque-transmitting mechanisms to provide seven forward speeds and one reverse speed.
Automatic shifting power transmissions are currently used in a majority of the vehicles produced in the United States. These vehicles generally employ three- and four-speed power transmissions. More recently, a trend towards more ratios, such as five- and six-speed power transmissions, has been proposed. In fact, some manufacturers do provide five-speed transmissions. Many of the vehicles utilizing manual type transmissions or countershaft type transmissions employ five- and six-speed power transmissions.
The five- and six-speed power transmissions provide improved vehicle acceleration performance and fuel economy when compared with three- and four-speed transmissions. Seven-speed transmissions offer further vehicle acceleration performance and fuel economy improvement over five- and six-speed transmissions. However, seven-speed power transmissions have not been proposed due to the complexity of these assemblies, as well as size and cost. There are many current patents that describe five- and six-speed power transmissions. Some of the six-speed power transmission patents, especially those assigned to the assignee of the present invention, describe six-speed power transmissions in families, wherein one or more family members incorporate a seven-speed power transmission.
It is an object of the present invention to provide an improved seven-speed power transmission having three planetary gearsets.
In one aspect of the present invention, each of the three planetary gearsets has first, second, and third planetary members.
In another aspect of the present invention, the first member of the first planetary gearset is continuously interconnected with the first member of the second planetary gearset through an interconnecting member.
In yet another aspect of the present invention, the first member of the third planetary gearset is continuously interconnected with a transmission housing or stationary member.
In still another aspect of the present invention, the output shaft of the transmission is continuously interconnected with at least one member of one of the planetary gearsets, and the input shaft is interconnected with members of the planetary gearsets only through individually-operated selectively-engageable torque transmitting mechanisms.
In yet still another aspect of the present invention, the input shaft is interconnected with members of the planetary gearsets only through individually-operated selectively-engageable torque-transmitting mechanisms.
In a further aspect of the present invention, six torque-transmitting mechanisms are incorporated with the three planetary gearsets.
In a yet further aspect of the present invention, a first and second of the torque-transmitting mechanisms are interconnected between the input shaft and at least one member of one of the planetary gearsets.
In a yet further aspect of the present invention, a third of the torque-transmitting mechanisms selectively interconnects a member of one of the planetary gearsets with the output shaft, or another member of one of the planetary gearsets.
In a still further aspect of the present invention, a fourth of the torque-transmitting mechanisms selectively interconnects a member the first or second planetary gearset with another member of one of the planetary gearsets.
In a yet still further aspect of the present invention, a fifth of the torque-transmitting mechanisms selectively interconnects a member of the second or third planetary gearset with another member of one of the planetary gearsets.
In a yet further aspect of the present invention, a sixth of the torque-transmitting mechanisms selectively interconnects a member of one of the planetary gearsets with another member of one of the planetary gearsets or with a transmission housing.
In a yet still further aspect of the present invention, the six torque-transmitting mechanisms are selectively engageable in combinations of four to establish at least seven forward speed ratios and one reverse speed ratio.
The present invention is found in a family of low-content seven speed transmission mechanisms requiring only three planetary gearsets and six selectively engageable torque-transmitting mechanisms. Each of the planetary gearsets has three members. Five of the torque-transmitting mechanisms are rotating type torque-transmitting mechanisms, while the sixth torque-transmitting mechanism, in some family members is a rotating type torque-transmitting mechanism, while in other family members it is a stationary type torque-transmitting mechanism.